Ci Shi

Magnetitum (Cishi) Magnetite Magnetite is a mineral of oxides of spinel group, containing mainly of ferroferric oxide (Fe3O4). The drug is collected, removed from foreign matter. Description Aggregates of masses, in irregular masses, or slightly subsquare, frequently with angularities. Greyish-black or brown; streak black, with lustre of metal. Texture hard and heavy, fracture uneven. Magnetic. Odour, earthy; tasteless. Identification To 0.1 g of the powder add 2 ml of hydrochloric acid, shake, allow to stand. The supernatant yields the reactions characteristic of ferric and ferrous salts (Appendix IV). Assay Heat to boil gently about 0.25 g of the fine powder, accurately weighed, in 15 ml of hydrochloric acid and 3 ml of 25% potassium fluoride solution in conical flask, covered with a watch glass. Add dropwise 6% stannous chloride solution, shake constantly until the drug is decomposed completely with only white residue left at the bottom of the flask. Stop to heat, wash the watch